Design considerations and cycling guidance for aluminum foil anodes in lithium-ion rechargeable cells

Al foil is an attractive anode candidate for Li-ion rechargeable batteries, but the systemic problem of fast capacity degradation limits its re-introduction in practical applications. Partial lithiation-delithiation does mitigate the issue to a certain degree, but the cycle life is still tied to the problems associated with the phase transformation between β-LiAl and α-Al. Utilizing the solubility range of β-LiAl has been proven to be a feasible approach to stabilize the β-LiAl grown on an Al foil, i.e., the β-LiAl(Al) anode, but the electrochemically driven ion transport limitations of this electrode remain largely unclear. Herein, we present comprehensive electrochemical analyses of the β-LiAl(Al) electrode to shed light on its kinetic limitations which have intrinsic links to the electrode thickness and total cell capacity. Results show that the β-LiAl(Al) electrode can be charged at a C-rate as high as 2.9 C when a proper prelithiation is done for an Al foil. The superior rate capability is suggested to partly originate from the fast lithium diffusion in β-LiAl: -10−7 cm2·s−1 at room temperature. Furthermore, the cells consisting of β-LiAl(Al) vs. commercial Li4Ti5O12 exhibit promising cycling performances, even at 10 mA·cm−2, giving 300 cycles with a capacity retention of ∼80%. With a systematic investigation of the limiting mechanisms focusing on correlating the prelithiation depth and the cycle life, the cyclability of the β-LiAl(Al) electrode at different current densities (0.5–10 mA·cm−2) is mapped out, providing comprehensive guidance for the practical utilization of the β-LiAl(Al) anode in a range of Li-ion cell types, from all-solid-state batteries to hybrid capacitors.